On the source and the course of the embryonic blood circulation during development in the warm-blooded Vertebralia / by W. Macdonald.

  • Macdonald, William, 1797-1875.
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: On the source and the course of the embryonic blood circulation during development in the warm-blooded Vertebralia / by W. Macdonald. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    ilio-cfecal valve iu man the colon ascends upwards to the lower surface. The abdominal aorta, though a single tube, may represent the double tube in the bird, and after giving off the inferior and superior mesenteric arteries before entering the thorax, gives off the splenic, gastric, and hepatic arteries to supply these important organs which mingle their venous blood with the portal, and thus combine to supply, along with the blood of the vente cava3, the sinus venosus. To return to the abdominal aorta—in passing through the diaphragm and giving off the phrenic arteries, it is again subdivided into two aorta3, passing up on each side of the spine as high as the fovea cardiaca, where they bend forward towards the sinus venosus, but a little behind and above, and so form two ter- minal branches meeting in the truncus arteriosus. Shortly after this union the right terminal aorta, as far as the thorax, is dwarfed off or absorbed, unless it is separated for the purpose of forming the pulmonary artery, which seems to be indicated, with the singular exception discovered in the dissecting theatre of l)r Handyside, which will be noticed in the Appendix. By this change the whole purified blood is conveyed to the truncus arteriosus by the left terminal branch of the aorta. The aortic terminal branches, from a subsequent ex- amination of tlie subject, seem to have been provided with what become the semilunar valve of the heart. The left terminal aorta seems to have exorcised or thrown off the lower branch, leaving it in the mesial plane of the thorax; and the small remains depending from the under curve of the aortic arch, led to the whole delusion of the ductus arteriosus, of which there is no existence in nature—the existence of what become the semilunar valves in all the terminal aortse, as well as the bulbus arteriosus, forming a horizontal three-starred valve, having prevented the escape of the blood into the cavity, and as it were forced the cur- rent to bound upwards into the arch of the aorta, with the arteries that supply the blood to the trunk and upper ex- tremities, and thus to continue the blood circulation during almost the whole period of embryonic life, till the requisite